Many manufacturing applications call for coupling two components together to form a watertight seal. For examples, many personal and commercial electronic devices (e.g., phones, watches, personal data assistants, audio playback devices, etc.) are manufactured such that the electronics are housed in a watertight enclosure. The enclosures may be formed using injection molding plastics, metals, or other materials commonly used in the manufacturing of miniature components, such as miniature thin wall housings.
To form the enclosure, typically, two or more enclosure components must be mechanically bonded together, with the electronic components contained therein, to form a watertight seal. Several bonding techniques may be used, such as high temperature laser welding, resistive welding, ultrasonic welding, or soldering. Typically, many of these bonding techniques employ a heat source and/or a pressure source to press the two or more enclosure components together at a seam location, while applying a bonding material, such as a metal or solder, to the seam area. In some applications, the edges of the enclosure components themselves may include the bonding material (e.g., the edge of the enclosure component may be made of metal). By applying pressure and/or heat to the bonding material, the bonding material may deform, causing the removal of oxidation and contaminant at the surface of the bonding material and enabling bond creation with the two or more enclosure components. For example, ultrasonic welding techniques typically employ an ultrasonic welding tool with an ultrasonic welding tip that vibrates at a high speed to generate heat.
When a hermetic seal is not required, many current welding techniques include applying heat to an enclosure while bringing two enclosure component halves together using a typical tongue and groove joint. In several of these applications, an energy director component may protrude from the end of the tongue, such that when the tongue is compressed against the valley of the groove in the presence of a heat source, the energy director deforms, removing oxidation and impurities to enable the creation of a bond. Typically, this bond occurs over a small surface area on the tongue, and thus, is typically not hermetic, and may not even be watertight.
In applications where a hermetic seal is required, current welding techniques may include using a shear joint, wherein a tongue structure on one enclosure component half is forced over an outer edge of a second enclosure component half, wherein a shear interface structure may protrude laterally outward from the edge of the second enclosure component half. As the tongue structure slides downward, over the edge of the second enclosure component half, it encounters the shear interface structure and causes the shear interface structure to deform (e.g, because of the shearing force being applied), while a heat source, such as a welding tool, applies heat to the interface. This deformation process may remove oxidation and impurities from the material in the shear interface structure, enabling bonding between the tongue and the edge of the second enclosure component half. The length of the shear interface component surface creates a substantial amount of surface area capable of forming a hermetic seal.
While current shear joint welding processes, similar to the process described above, are capable of creating a hermetic seal between two component halves, they generally require precise alignment of the two component halves that requires a supporting fixture to be used with at least one of the component halves. Moreover, the requirement for such precise alignment also results in lower yields due to variances in component dimensions and placement during the welding process. Accordingly, these current hermetic seal welding processes depend on maintaining tight tolerances.